Armstrong, IA frost dates
Last spring frostMay 4median date
First fall frostOct 1median date
Growing season150 daysfrost-free
Hardiness zone5aZone 5a
How Armstrong compares
- In 8 years out of 10, the last spring frost in Armstrong falls between April 21 and May 14, a 23-day window. The first fall frost falls between September 18 and October 15.
- The median last frost is 6 days later than the Iowa median of Apr 28.
- Its 150-day growing season is among the shortest of the 934 Iowa places with a regular frost season.
- The last frost is typical for zone 5a, where the median is May 3.
- The weather station records an average of 163 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 21 |
| 50% (median) | May 4 |
| 10% (safe for tender plants) | May 14 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 18 |
| 50% (median) | October 1 |
| 90% (late) | October 15 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Armstrong, IA
Armstrong, IA frost dates — last frost May 4, first frost Oct 1, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 9 to Feb 23Transplant outside: Apr 6 to Apr 20
Start indoors: Feb 23 to Mar 9Transplant outside: May 18 to Jun 1
Start indoors: Feb 23 to Mar 9Transplant outside: May 18 to Jun 1
Start indoors: Mar 9 to Mar 23Transplant outside: May 11 to May 25
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 13 to Apr 27Sow outdoors: Apr 6 to May 11Plant for fall: Aug 6 to Sep 3
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 6 to Apr 20Sow outdoors: Apr 6 to Apr 20Plant for fall: Jul 23 to Aug 13
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 20 to May 4Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 13 to Apr 27Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 20 to May 4Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 23 to Apr 6Transplant outside: May 25 to Jun 8Sow outdoors: May 25 to Jun 8
Start indoors: Mar 23 to Apr 6Transplant outside: May 11 to May 25
Sow outdoors: Mar 23 to Apr 13Plant for fall: Jul 9 to Jul 30
Sow outdoors: Mar 23 to Apr 13Plant for fall: Aug 6 to Aug 27
Sow outdoors: Mar 30 to May 11Plant for fall: Aug 20 to Sep 10
Start indoors: Apr 6 to Apr 13Transplant outside: May 18 to May 25Sow outdoors: May 11 to May 25Plant for fall: Jul 16 to Jul 30
Start indoors: Apr 6 to Apr 13Sow outdoors: May 11 to May 25Plant for fall: Jul 23 to Aug 6
Start indoors: Apr 6 to Apr 13Sow outdoors: May 11 to May 25
Start indoors: Apr 6 to Apr 13Transplant outside: May 18 to Jun 1
Sow outdoors: Apr 13 to May 11Plant for fall: Jul 9 to Jul 23
Sow outdoors: Apr 13 to May 11Plant for fall: Jul 23 to Aug 6
Sow outdoors: Apr 13 to May 4
Sow outdoors: Apr 20 to May 18Plant for fall: Jul 23 to Aug 6
Sow outdoors: Apr 20 to May 11Plant for fall: Aug 6 to Aug 27
Sow outdoors: May 11 to Jun 1Plant for fall: Jul 16 to Jul 30
Sow outdoors: May 11 to May 25
Transplant outside: May 18 to Jun 8
Plant for fall: Sep 17 to Oct 22
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Armstrong, IA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 9 – Feb 23 | Apr 6 – Apr 20 | — | — |
| Peppers | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Eggplant | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Tomatoes | Mar 9 – Mar 23 | May 11 – May 25 | — | — |
| Lettuce | Mar 9 – Mar 23 | Apr 13 – Apr 27 | Apr 6 – May 11 | Aug 6 – Sep 3 |
| Kale | Mar 9 – Mar 23 | Apr 6 – Apr 20 | Apr 6 – Apr 20 | Jul 23 – Aug 13 |
| Broccoli | Mar 9 – Mar 23 | Apr 20 – May 4 | — | Jun 25 – Jul 16 |
| Cabbage | Mar 9 – Mar 23 | Apr 13 – Apr 27 | — | Jun 25 – Jul 16 |
| Cauliflower | Mar 9 – Mar 23 | Apr 20 – May 4 | — | Jun 25 – Jul 16 |
| Okra | Mar 23 – Apr 6 | May 25 – Jun 8 | May 25 – Jun 8 | — |
| Basil | Mar 23 – Apr 6 | May 11 – May 25 | — | — |
| Peas | — | — | Mar 23 – Apr 13 | Jul 9 – Jul 30 |
| Spinach | — | — | Mar 23 – Apr 13 | Aug 6 – Aug 27 |
| Radishes | — | — | Mar 30 – May 11 | Aug 20 – Sep 10 |
| Cucumbers | Apr 6 – Apr 13 | May 18 – May 25 | May 11 – May 25 | Jul 16 – Jul 30 |
| Zucchini & Summer Squash | Apr 6 – Apr 13 | — | May 11 – May 25 | Jul 23 – Aug 6 |
| Winter Squash & Pumpkins | Apr 6 – Apr 13 | — | May 11 – May 25 | — |
| Melons & Watermelon | Apr 6 – Apr 13 | May 18 – Jun 1 | — | — |
| Carrots | — | — | Apr 13 – May 11 | Jul 9 – Jul 23 |
| Beets | — | — | Apr 13 – May 11 | Jul 23 – Aug 6 |
| Potatoes | — | — | Apr 13 – May 4 | — |
| Swiss Chard | — | — | Apr 20 – May 18 | Jul 23 – Aug 6 |
| Cilantro | — | — | Apr 20 – May 11 | Aug 6 – Aug 27 |
| Green Beans | — | — | May 11 – Jun 1 | Jul 16 – Jul 30 |
| Sweet Corn | — | — | May 11 – May 25 | — |
| Sweet Potatoes | — | May 18 – Jun 8 | — | — |
| Garlic | — | — | — | Sep 17 – Oct 22 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Swea City 5n, IA weather station, 16 km away (elevation 1,181 ft (360 m)).
Frost dates near Armstrong
- Ringsted May 2 · Oct 3
- Dolliver May 2 · Sep 30
- Swea City May 4 · Oct 1
- Fenton Apr 30 · Oct 6
- Bancroft May 4 · Oct 1
- Wallingford May 2 · Oct 3
- Estherville May 2 · Oct 3
- Ledyard May 4 · Oct 1
- Graettinger Apr 27 · Oct 7
- Cylinder Apr 27 · Oct 7
Frequently asked questions
When is the last frost in Armstrong, IA?
The median last spring frost in Armstrong, IA is May 4. There is still about a 10% chance of frost after May 14, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Armstrong, IA?
The median first fall frost is October 1, with about a 10% chance of frost before September 18.
How long is the growing season in Armstrong, IA?
About 150 days between the median last spring frost and first fall frost.
What planting zone is Armstrong, IA?
Armstrong, IA is in USDA hardiness zone 5a.